man2/getunwind.2

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   2 .\" Written by Marcela Maslanova <mmaslano@redhat.com>
   3 .\" and Copyright 2013, Michael Kerrisk <mtk.manpages@gmail.com>
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   7 .TH getunwind 2 (date) "Linux man-pages (unreleased)"
   8 .SH NAME
   9 getunwind \- copy the unwind data to caller's buffer
  10 .SH LIBRARY
  11 Standard C library
  12 .RI ( libc ", " \-lc )
  13 .SH SYNOPSIS
  14 .nf
  15 .B #include <linux/unwind.h>
  16 .BR "#include <sys/syscall.h>" "      /* Definition of " SYS_* " constants */"
  17 .B #include <unistd.h>
  18 .PP
  19 .BI "[[deprecated]] long syscall(SYS_getunwind, void " *buf \
  20 ", size_t " buf_size );
  21 .fi
  22 .SH DESCRIPTION
  23 .I Note: this system call is obsolete.
  24 .PP
  25 The
  26 IA-64-specific
  27 .BR getunwind ()
  28 system call copies the kernel's call frame
  29 unwind data into the buffer pointed to by
  30 .I buf
  31 and returns the size of the unwind data;
  32 this data describes the gate page (kernel code that
  33 is mapped into user space).
  34 .PP
  35 The size of the buffer
  36 .I buf
  37 is specified in
  38 .IR buf_size .
  39 The data is copied only if
  40 .I buf_size
  41 is greater than or equal to the size of the unwind data and
  42 .I buf
  43 is not NULL;
  44 otherwise, no data is copied, and the call succeeds,
  45 returning the size that would be needed to store the unwind data.
  46 .PP
  47 The first part of the unwind data contains an unwind table.
  48 The rest contains the associated unwind information, in no particular order.
  49 The unwind table contains entries of the following form:
  50 .PP
  51 .in +4n
  52 .EX
  53 u64 start;      (64\-bit address of start of function)
  54 u64 end;        (64\-bit address of end of function)
  55 u64 info;       (BUF\-relative offset to unwind info)
  56 .EE
  57 .in
  58 .PP
  59 An entry whose
  60 .I start
  61 value is zero indicates the end of the table.
  62 For more information about the format, see the
  63 .I IA-64 Software Conventions and Runtime Architecture
  64 manual.
  65 .SH RETURN VALUE
  66 On success,
  67 .BR getunwind ()
  68 returns the size of the unwind data.
  69 On error, \-1 is returned and
  70 .I errno
  71 is set to indicate the error.
  72 .SH ERRORS
  73 .BR getunwind ()
  74 fails with the error
  75 .B EFAULT
  76 if the unwind info can't be stored in the space specified by
  77 .IR buf .
  78 .SH VERSIONS
  79 This system call is available since Linux 2.4.
  80 .SH STANDARDS
  81 This system call is Linux-specific,
  82 and is available only on the IA-64 architecture.
  83 .SH NOTES
  84 This system call has been deprecated.
  85 The modern way to obtain the kernel's unwind data is via the
  86 .BR vdso (7).
  87 .SH SEE ALSO
  88 .BR getauxval (3)